Detroit Diesel Allison CD 850 6A (Transmission)

NAVAIR 17-15-50.4

TM 38-301-4

T.O. 33-1-37-4

CGTO 33-1-37-4

COMPONENT:

Detroit Diesel Allison CD 850 6A (Transmission)

LUBRICANT: MIL-L-2104

Normal Range

0-150

0-15

0-13

0-5

0-180

0-28

0-13

0-100

151-

181-

101-

Marginal Range

16-22

14-18

6-7

29-36

14-18

205

255

140

206-

256-

141-

High Range

23-30

19-25

8-9

37-45

19-25

260

325

175

Abnormal

261+

31+

26+

10+

326+

46+

26+

176+

Abnormal Trend

(PPM Increase

in 10 hrs)

TECHNICAL INFORMATION

When silver (Ag) and iron (Fe) are increasing excessively and at

approximately the same rate, the silver-plated bushings (Part No.

7539858) in the steer differential pinion are wearing excessively.

When silver (Ag) only is rapidly increasing, the silver-plated seal

ring (Part No. 8352004) in the main oil pump may be wearing

excessively, and the pump pressure should be monitored closely.

Some of the brake and clutch plates in the transmission are

sintered bronze. When the iron and copper in the transmission are

increasing at approximately the same rate, the plates may need

adjustment, but are probably in good condition. On the other

hand, if the iron wear rate exceeds the copper wear rate, the plates

are probably worn excessively, and the transmission may fail.

This is because the plates are worn through and the iron is coming

from the backing plates. In a new transmission, the copper may

run as high as 300 PPM with a much lower iron count until the

transmission has worn-in and the fluid has been changed.

When the rear main oil seal in the AVDS 1790 engine wears

excessively or ceases to function properly, there will be cross-

contamination of the engine and transmission (CD-850-6A)

lubricants. This, in general, will be indicated by increasing or

high molybdenum (Mo) in the transmission oil samples and high

copper and lead in the engine oil samples.

Transmission is air-cooled;

therefore,

liquid-coolant

contamination problems.

Wear of bushings is normally minimal.

B-84